Problem: $\dfrac{1}{10} - \dfrac{8}{5} = {?}$
Answer: $ = {\dfrac{1 \times 1}{10 \times 1}} - {\dfrac{8 \times 2}{5 \times 2}} $ $ = {\dfrac{1}{10}} - {\dfrac{16}{10}} $ $ = \dfrac{{1} - {16}}{10} $ $ = -\dfrac{15}{10}$